SIBTOSA HYBRIDS (TETRAPLOID)Hybrids with 4n=66 chromosomes, which can be derived from the same species as diploid Sibtosa hybrids, but have double the number of chromosomes and, therefore, larger flowers. They can either be produced directly by colchicine treatment or as a result of crosses between tetraploid parent plants. Such hybrids are fertile: in the process of the reduction of chromosome numbers during the production of sexual cells each chromosome, due to the tetraploid structure, finds an analogue counterpart chromosome of its own kind.